As Shown in the Figure, Three Charges Are at the Vertices

As shown in the figure, three charges are at the vertices of an equilateral triangle. The charge $Q$ is $6.7 \mathrm { nC }$ , and all the other quantities are accurate to two significant figures. What is the magnitude of the net electric force on the charge $Q$ due to the other two charges? $\left( k = 1 / 4 \pi \varepsilon _ { 0 } = 9.0 \times 10 ^ { 9 } \mathrm {~N} \right.$ . $m ^ { 2 } / C ^ { 2 }$ )

A) $1.4 \times 10 ^ { - 3 } \mathrm {~N}$
B) $1.0 \times 10 ^ { - 3 } \mathrm {~N}$
C) $2.1 \times 10 ^ { - 3 } \mathrm {~N}$
D) $1.2 \times 10 ^ { - 3 } \mathrm {~N}$